Need a little help on my Spectrum Analyzer. It's pretty much done but I'm stuck.

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Colin il 25 Apr 2014

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https://it.mathworks.com/matlabcentral/answers/127091-need-a-little-help-on-my-spectrum-analyzer-it-s-pretty-much-done-but-i-m-stuck

Modificato: Image Analyst il 25 Apr 2014

Hi, I'm new to MatLab and I'm trying to build a spectrum analyzer. I think I have most of it but I can't get it to work. I was hoping someone could glance at it to see if it was something obvious. Thanks for any help.

The script is at the bottom

This is the function:

function y = CPetty_spectrumAnalyzer( filename, winLength, overlapLength, window, fftlength)
%Input 
%filename: name of .WAV file to be analyzed 
%winLength: length of signal window (in samples) 
%overlapLength: length of signal overlap (in samples) 
%window: window type: passes one of the following strings 
% ‘rect’ 
% ‘hamming’ 
% ‘hann’ 
% ‘blackman’ 
% ‘bartlett’ 
%fftlength: number of samples to be used in fft (default: winLength) 
%Output 
%y : a 2D matrix containing the normalized magnitudes of the STFT in dB
%If the user did not input 5 arguments total...
if (nargin ~= 5);
disp('You have to enter 5 arguments (filename,winLength,overlapLength,window,fftlength ')
end
%If the user trys to name the file with numbers and symbols
if ~isstr(filename)
error('The filename has to be letters with single quotes around it')
end
%If the overlap value is greater than the window length.
if (overlapLength > winLength)
error('The overlap value cant be longer than the window length')
end
%Since the fftlength uses the samples in the windows, it can't be less
%than the window length.
if fftlength < winLength,
error('The fftlength cant be less than the winLength')
end
if (winLength < 1), abs(winLength);
disp('You cant use negative numbers, I made them positive for you')
end
if (overlapLength < 1), abs(overlapLength);
disp('You cant use negative numbers, I made them positive for you')
end
if (fftlength < 1), abs(fftlength);
disp('You cant use negative numbers, I made them positive for you')
end
if (mod(winLength, 1) ~= 0)||(mod(overlapLength, 1) ~= 0)||(mod(fftlength, 1) ~= 0); 
disp('Lengths cant be floating points. I rounded them up to the next integer')
end
switch window 
case 'rect' 
win = rect(winLength);
case 'hamming' 
win = hamming(winLength); 
case 'hann' 
win = hann(winLength); 
case 'blackman' 
win = blackman(winLength); 
case 'bartlett' 
win = bartlett(winLength); 
otherwise 
error('rect, hamming, hann, blackman or bartlett'); 
end
%Load the file and store the audio in x and the samplerate in fs.
[x, fs] = wavread(filename); 
%To make a stereo file mono, the mean is calculated.
x = mean(x, 2);
%Make the hop size the difference between the window and overlap lengths.
hop = winLength - overlapLength;
%To buffer the signal to the right window and overlap lengths.
buf = buffer(x, winLength, overlapLength);
%K is the number of frames that are needed for the function.
K = ceil(length(x)/hop); 
%To create a matrix by tiling.
winMat = repmat(win, 1, K);
%Matrix multiplication for each frame of audio by each window function.
winBuf = buf .* winMat; 
%FFT of the windowed signal.
fftBuf = fft(winBuf, fftlength); 
%Find the normalized magnitudes of the post STFT signal in Db.
magnitudes = 20*log10(abs(fftBuf) / (fftlength/2));
%Find the ammount of information that's in the bin.
NyqBin = (length(magnitudes)/2) + 1;
end
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
y = CPetty_spectrumAnalyzer('testSig.wav', 1024, 512, 'hann');
[x, fs] = wavread('testSig.wav');
dur = length(x) / fs;
time = linspace( 0, dur, size(y, 2) );
freqs = linspace( 0, fs/2, size(y,1)+1 ); 
imagesc(time, freqs, y);
axis( 'xy' )
xlabel('Time (s)');
ylabel('Frequency (Hz)');
title('Spectogram');
colormap('Autumn')
f = figure;
movegui(f,'center');
imagesc(time, freqs, y);
axis( 'xy' ) %Flip axes 
xlabel('Time (s)');
ylabel('Frequency (Hz)');
ylim([0 8000]); % Limit y axis to 8kHz
title('Spectogram result for 0 - 8kHz.')
colormap('Autumn');